A prior art stump cutting machine is described in U.S. Pat. No. 2,912,022. A prior art stump cutting tooth structure is described in U.S. Pat. No. 4,759,394, issued July 26, 1988 to Lyle J. Clemson. The prior art stump cutting structure machine includes a rotatable circular blade having a plurality of tooth and holder assemblies mounted on the blade at the periphery thereof, each tooth and holder assembly including a tooth holder mounted at one side of the circular blade adjacent to the periphery, said holder having a flat face held parallel against said blade, said face of said holder having a slot therein radially of said blade, a cutting tooth having a shank portion and a cutting head portion, said head portion having a carbide cutting tip, said shank portion being disposed in said holder slot, being held against said blade by opposite clamping forces, said tooth head portion extending outwardly of said slot and radially of said blade, said head portion being angled transversely of said shank portion outwardly of said slot, and said head portion being twisted axially of said shank portion.
One problem with the prior art stump cutting tooth structure is that excess stress, due to shear load, bending moments and torsion moments, have caused failure at the region of the tooth where the shank portion joins the head portion. A second problem is the fracturing of the tooth holders and holder bolts during operation. A third problem can develop at impact as the head portion of the tooth is twisted axially. Shear loading transverse to the plane of the shank portion often occurs which can result in the loss of the carbide tip.
A fourth problem involves the difficulty in removing prior art teeth from the holder assembly, especially after use.
Still another problem occurs due to the presence of moment loads resulting from the angled carbide tip portion of the tooth. These moment loads can cause the tooth to dislodge from the holder.